This project will involve investigation of the specific binding of serotonin and various adrenergic and cholinergic neurotransmitter substances to rodent intestinal villus and crypt epithelial cells. In addition, the same agents (in the absence and presence of various antagonist drugs, will be tested for their ability to stimulate adenylate and guanylate cyclase and Na/K ions ATPase. The overall objective is to determine if specific receptors for the agents exist on the cells and to "couple" (relate) this to alterations in one or more of the enzyme systems. These enzymes are established as modifiers of ion transport in the intestine, hence by these studies we might better understand intestinal secretory mechanisms and diarrheas of neurogenic origin. Methods will involve vibrating the cells from everted intestinal segments and collecting the pellets for homogenization and measurement of ligand binding (with high specific activity, tritiated ligands) by filtration. Enzyme activities will be determined using 32p-alpha-ATP, 32p-alpha-GTP and 32P-gamma-ATP.